Yes, the Harmony 650 or better Harmony models will work. What you do is build a extra activity called 'Watch Smart Hub' that uses the TV and LG home theater. The input on the TV doesn't need to be set, but home theater should be set for TV audio. Then assign a soft key to Smart Hub command.

Optionally you can add the SmartHub command to starting the activity and Exit, Exit for activity end. Given the layout it's best the 'Watch Smart Hub' be the 4th activity on a Harmony 650. Also add the cable box (if used) to the activity and reassign the channel up, channel down to the cable box.